There have been several recent reports in animals AND people that seem to indicate that high-intensity/high volume exercise done over 20-30 years might be bad! A recent NY Times blog has brought this idea to the forefront:”Spending more years exercising strenuously or completing more marathon or ultramarathon races was, in this study, associated with a greater likelihood of heart damage.”¹ The study group was made of 12 men (age > 50 years) with lifetime histories of endurance competition (and no co-morbidities that might influence the outcome of the study). While previous studies have seen this type of damage (fibrosis in the heart) they could not control for confounding factors, for example, lifestyle risk factors such as diet, smoking, taking up exercise in later years, etc. The Marathon Club members (in this study – completed 100 marathons or ultra-marathons > 50 miles) on the other hand started young and continued training and competing over their
lifetime http://www.ncbi.nlm.nih.gov/pubmed/21330616s When their hearts were imaged with Cardiac Magnetic Resonance (specific to the heart) 50 % of the marathoners showed signs of fibrosis.
It is important to note that 1) there were only 12 men in this study, 2) they were men (no data on women), and 3) they were asymptomatic (no signs of problems).
In rats, a 16 week regimen of vigorous exercise caused remodeling (changes to the heart make-up) that made them easy to experience arrhythmias (irregular heart beats) when provoked (caused) by the researchers. The good news is 8 weeks of rest (detraining) returned their hearts to normal. http://circ.ahajournals.org/cgi/content/short/123/1/13
That doesn’t mean that the same thing will happen in humans of course since rats ≠ people!
Like all good research more questions are generated than solved! And that is the beauty of research! If you think you know the definitive answer to something, you probably are fooling yourself! Of course there may be exceptions in chemistry, physics, and the like where you can totally control the research environment. However, human organisms are very complex and as you know hard to control! 🙂
So what does this mean to the average person trying to get or be fit? Probably not much since 99.9% of the population will never reach the training intensity or volume of these groups! There are so many positive benefits of physical movement, for example, lowering risk for heart disease, some cancer, diabetes, arthritis, obesity, etc. that it wouldn’t make sense to say it is bad! Most of the population can benefit from regular exercise and proper nutrition. The bottom line is if you are exercising don’t stop and if you don’t exercise start!
For more information about starting an exercise program or when you should seek healthcare advice visit the American College of Sports Medicine website http://www.acsm.org/